Manchester United versus Liverpool will always be one of the key rivalries in English football. The balance of power in the north-west is something the rest of the game finds impossible to ignore, so that, even if José Mourinho guides Chelsea to another league title this season, there will still be people convinced he would have been much happier at Old Trafford.

Part of the allure, at least in recent decades, has been the unprecedented level of dominance each side has achieved when in the ascendancy. Brilliant as Mourinho undoubtedly is, he will have to go some at Chelsea to match the staggering list of Liverpool accomplishments in the 70s and 80s, or turn an 18-7 title deficit into a 20-18 lead in the space of 20 years.

Sir Alex Ferguson did not just knock Liverpool off their perch, he left them spitting feathers. Small wonder David Moyes is finding it hard to be quite as ruthless but what gives Sunday's encounter its special piquancy is not just that United might be on the slide but that Liverpool appear to be on the rise. Steven Gerrard said at the start of the season that he did not expect to be in a position to win a title in the playing years still left to him. He did not think Liverpool could mount a serious challenge quickly enough and he will have been delighted to have been proved wrong.

Liverpool may not win the title this season, may not even beat United this afternoon, but they are certainly mounting a serious challenge. But for Mourinho coming back to London they would be out in front by now, with not only more points but more goals scored than anyone else.

Ferguson could not have envisaged that happening, though it might be a mistake to imagine it is only the old fire‑breather's departure that has given Liverpool their chance. Brendan Rodgers took over at Anfield with a remit for gradual, sustainable improvement and the Liverpool manager claims that, while results were not instant, the graph began to curve upwards before the end of last season. "If you look at the last 38 games, the 10 from the end of last season and the 28 we have played in the league since, which would be a full season worth of games, we would be 12 points ahead of Manchester United with 91 goals scored opposed to 64," Rodgers says. "So over that period, including Fergie's time as well, we have shown progress. That's all I'm saying. We are going there to win, not to kill off their Champions League hopes or open up a bigger gap. We are looking upwards rather than downwards and we feel we have a great chance in every game we play. I'm not going to be shouting about winning the league. That is not the dignified way to do it. It's not mind games or anything like that. It's just letting the players do the talking. That's what they have done."

No one has talked louder, in this metaphorical sense at least, than 24-goal Luis Suárez. Rodgers inherited a player who kept talking himself into trouble, whether upsetting Patrice Evra with racial remarks or making it clear last summer that he would rather be playing Champions League football. But Liverpool kept him to his contract, encouraged him to concentrate on his football and play as a member of a team rather than as an individual and have never looked back.

Even Moyes in the United camp is prepared to acknowledge the significance of Suárez's season. "It was a major coup for Liverpool when they kept Suárez," Moyes says. "I think that was a real big deal for them. It has really worked to their advantage. Daniel Sturridge has done really well too and Raheem Sterling, they have a really good attacking force."

Arsenal can vouch for that – and Tottenham. And while United have a big game against Olympiakos to worry about this week, Liverpool arrive fresh and rested after a weekend off. Suárez can expect some stick from the Old Trafford crowd but Rodgers is sure he will cope with it. "Don't underestimate Luis. He's a hard man," the Liverpool manager says. "We've seen plenty of hard men in football over the years but they are usually tough, aggressive centre-halves or midfield players who put their foot in.

"Luis is a striker but he is a hard man. He gets battered, he gets kicked, he gets baited by opposing supporters but he is the toughest player mentally I've ever come across and I've worked with some big players. He is relentless in his desire. We've all seen that in his time here and now he is more mature as well, which is great. There's not much rattles him and playing at Old Trafford will only inspire him."

Naturally Rodgers thinks Suárez should be a contender for the player of the season awards. "Some players have been outstanding this year but I think the way Luis has played, after everything he has gone through, means he would be very deserving of it." Few would disagree for, while what Suárez has gone through was all his own doing and should not really influence the judges, what he has produced on the pitch ought to be enough and there is probably more to come.

"We won a big battle to keep him here.There was a lot of work to convince him that the club was going forward," Rodgers says. "Everyone was determined and happily it all worked out. You never know what will happen this summer, with it being a World Cup year, but Luis was happy to sign a new contract and he'll continue to play a lead role in what we are trying to do here. We haven't got money like Chelsea or Manchester City. We have to develop players and do it through coaching. I think that's why people enjoy watching us. It's great to be regarded as everyone's second- favourite team but we will see over the next 10 games what we are capable of."